A common death causing failure of mammals such as human beings is a heart failure caused by occlusion of the coronary arteries of the heart. An occlusion in the coronary artery reduces the flow of blood to the heart muscle which loses its contractibility and hence, its pumping capacity. The victim then goes into cardiogenic shock whereby the heart progressively loses its ability to pump blood. This progressive loss of pumping ability occurs because the heart receives its blood supply through the coronary arteries only during its resting phase. When there is a blockage and an area of the heart muscle loses its ability to pump, the victim's systolic and diastolic blood pressures are reduced. The diastolic pressure is that pressure maintained in the arteries during the time that the heart is resting and is what causes blood to flow through the coronary arteries to nourish the heart. Since the weakened heart during an attack causes the diastolic pressure to be below its normal point, the heart receives less and less nourishment which causes more and more area of the heart muscle to be involved in the attack. This cumulative process if unchecked causes death when the heart can no longer sustain itself.
It should be noted that in most cases of coronary occlusion, sufficient heart muscle remains to pump some blood although it may not be an adequate blood flow to prevent cardiogenic shock. A device to assist the heart during this critical period is desirable, an example of which is the balloon type pneumatic pumping machine produced by the Datascope Company of Saddle Brook, New Jersey and described in U.S. Pat. No. 3,692,018. In this device a properly sized inflatable balloon is inserted into the patient's arterial system through an incision made in the groin. The balloon is then fed upwardly through the femoral artery to the aorta and maintained in position just below the carotid arteries. Through the use of EKG signals and appropriate controls, the balloon is caused to inflate and contract, to counter-pulsate the heart. This withdraws or receives blood from the left ventricle of the heart during systole and injects or replaces blood into the aorta during diastole. To make the proper adjustments to this pulsation cycle, the blood pressure of the victim must be sensed and compared as the various controls on the Datascope device are adjusted. The blood pressure is normally sensed by inserting a tube into a wrist artery. This common procedure has many disadvantages; the most important of which being that at a very critical time, where no time should be wasted, it can take as much as 20 minutes to perform. Pressure sensing tubes in such wrist arteries are not desirable for other reasons as well. They tend to cause clots because of their large relative size to the blood flow thereabout and therefor must be replaced or moved every two to three days. Also, the pressure sensed is not the pressure in the aorta but some different pressure that is attenuated and phased by the arterial tree between the aorta and the wrist. If the desired aorta pressure data was available, such also could be used to assure proper positioning of the ballon before the Datascope device is activated, thus reducing the changes that it is activated with a portion of the ballon in a carotid artery, which might kill the patient. Therefore, there has been a continuing need to provide means to sense the aorta pressure which do not tend to clog, which take no time to insert and which remain accurate over an extended length of time. It has also been desired to provide means to assure a doctor that he is inserting the aforementioned ballon in the correct position within the aorta.